The present invention relates generally to overhead transmission conductors and particularly to a conductor that has reduced drag when non-laminar (i.e., turbulent) air flows across the conductor.
In areas of the world subject to hurricanes and like phenomena, drag on overhead transmission line conductors, when subjected to high velocity winds, becomes a very important consideration in the design of transmission lines. Hence, over the years, there have been many attempts to design overhead conductors that have reduced wind drag.
A recent conductor structure and design in this area is disclosed in U.S. Pat. No. 4,356,346 to Sakabe. Sakabe employs a plurality of segmented conductor elements disposed annularly about a core of the conductor. Outside corners of the conductors are provided with a radius that forms circumferentially spaced and longitudinally extending grooves. Such grooves are stated as being effective to reduce the coefficient of drag in terms of the Reynolds Number used in designing conductors. The Reynolds Number is a factor that is dependent upon the diameter of the conductor, the velocity of the air moving across the conductor, and kinematic viscosity. The Reynolds Number (N.sub.R)can be expressed as follows: ##EQU1## Kinematic viscosity varies with atmospheric pressure and temperature. Kinematic viscosity is equal to:
Similar structures and analyses are presented in two papers entitled respectively "On the Reduction of Wind Loading Overhead Transmission Line" by S. Sakabe et al, and "Development of Low Wind Pressure Conductors for Compact Overhead Transmission Line" by A. Sakakibara et al. The first paper is Report No. 111-04 published by the International Conference on Large High Voltage Electric Systems, while the second paper is a report by the IEEE, numbered 84WM228-3.